<?php
header("Content-type:image/jpeg");
//绘制画布
$img =imagecreatetruecolor(400,400);

//定义颜色 
$blue=imageColorAllocate($img,0,0,255);
$red=imageColorAllocate($img,255,0,0);

imageFill($img,0,0,$red);
imageEllipse($img,200,200,100,100,$blue);
imagejpeg($img);